Himalayan rivers play a significant role in the survival of the vast population of the Indian subcontinent. Information on the long-term spatio-temporal hydrological variability is required for hydropower generation, irrigation, and flood management. Therefore, there is an urgent need to understand the long-term perspective of the flow of these rivers (also considered as streamflow) which could only be achieved based on proxy data analysis in the absence of observed data. Tree-rings provide an excellent proxy of streamflow to understand the hydrologic variations for a long past beyond the existing instrumental records. The logic behind developing the relationship between tree growth and streamflow is the common climatic factors, mainly precipitation and evapotranspiration controlling the tree growth and streamflow. Here, this chapter presents a review of the available information of tree-ring-based streamflow records and flood events from some of the Himalayan rivers along with fundamental principles followed for the analysis of discharge reconstructions.